A Convenient Synthesis of 2,3‐Dihydro‐4H‐thiopyrano[2,3‐b]‐, ‐[2,3‐c]‐, or ‐[3,2‐c]pyridin‐4‐ones by the Reaction of the Corresponding 1‐(Chloropyridinyl)alk‐2‐en‐1‐ones with NaSH |
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Authors: | Kazuhiro Kobayashi Ayumi Imaoka |
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Institution: | Division of Applied Chemistry, Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4‐101 Koyama‐minami, Tottori 680‐8552, Japan, (phone/fax: +81(857)315263) |
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Abstract: | 2,3‐Dihydro‐4H‐thiopyrano2,3‐b]pyridin‐4‐ones 4 were prepared by a three‐step sequence from commercially available 2‐chloropyridine ( 1 ). Thus, successive treatment of 1 with iPr2NLi (LDA) and α,β‐unsaturated aldehydes gave 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ols 2 , which were oxidized with MnO2 to 1‐(2‐chloropyridin‐3‐yl)alk‐2‐en‐1‐ones 3 . The reactions of 3 with NaSH?n H2O proceeded smoothly at 0° in DMF to provide the desired thiopyranopyridinones. Similarly, 2,3‐dihydro‐4H‐thiopyrano2,3‐c]pyridin‐4‐ones 8 and 2,3‐dihydro‐4H‐thiopyrano3,2‐c]pyridin‐4‐ones 12 were obtained starting from 3‐chloropyridine ( 5 ) and 4‐chloropyridine ( 9 ), respectively. |
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Keywords: | 4H‐Thiopyranopyridin‐4‐ones 2 3‐dihydro‐ Pyridines chloro‐ |
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